Ch.25 - Recognizing Some Common Causes of Intracranial Pathology Flashcards
1
Q
Study of 1st choice in acute head trauma:
A
UNENHANCED CT - Search for findings should initially focus on finding mass effect on blood.
2
Q
Linear skull fractures:
A
Important mainly for the intracranial abnormalities that may have occurred at the time of the fracture.
3
Q
Depressed skull fractures:
A
Can be associated with underlying brain injury and may require elevation of the fragment.
4
Q
Basilar skull fractures:
A
More serious - Can be associated with CSF leaks.
5
Q
Blow-out fractures of the orbit:
A
Result from direct blow and may present with orbital emphysema, fracture through either the floor or medial wall of the orbit, and entrapment of fat and extraocular muscles in fracture.
6
Q
4 types of intracranial hemorrhage associated with trauma:
A
- Epidural hematoma.
- Subdural hematoma.
- Intracerebral hemorrhage.
- Subarachnoid hemorrhage.
7
Q
Almost all (95%) epidural hematomas are associated with:
A
Skull fractures.
8
Q
ACUTE epidural hematomas appear as:
A
Hyperintense collections of blood that typically have a lenticular shape.
9
Q
As they age - epidural hematomas become:
A
HYPODENSE to normal brain.
10
Q
Subdural hematomas most commonly result from:
A
Deceleration injuries or falls.
11
Q
Subdural hematomas are:
A
Crescent-shaped bands of blood that may cross suture lines and enter the interhemispheric fissure –> THEY CANNOT CROSS THE MIDLINE.
12
Q
Subdural hematomas are typically:
A
Concave INWARD to the brain and may appear isointense (isodense) to the remainder of the brain as they become subacute and hypodense when chronic.
13
Q
Traumatic intracerebral hematomas:
A
Are frequently from shearing injuries and present as petechial or larger hemorrhages in the frontal or temporal lobes.
14
Q
Traumatic intracerebral hematomas may be associated with:
A
Increased intracranial pressure and brain herniation.
15
Q
Brain herniations include:
A
- Subfalcine.
- Transtentorial.
- Foramen magnum/tonsillar.
- Sphenoid.
- Extracranial herniations.
16
Q
Diffuse axonal injury is:
A
A SERIOUS consequence of trauma in which the corpus callosum is most commonly affected.
17
Q
Diffuse axonal injury - CT findings:
A
Similar to those for intracerebral hemorrhage following head trauma.
18
Q
Diffuse axonal injury - Study of choice:
A
MRI.
19
Q
In general, increased intracranial pressure is due to:
A
- Increased volume of the brain (cerebral edema).
2. Increased size of the ventricles (hydrocephalus).
20
Q
2 major categories of cerebral edema:
A
- Vasogenic.
2. Cytotoxic.
21
Q
Vasogenic edema:
A
Represents extracellular accumulation of fluid and is the type that occurs with:
- Malignancy.
- Infection.
22
Q
Vasogenic edema affects the … matter more.
A
WHITE MATTER.
23
Q
Cytotoxic edema:
A
Represents cellular edema –> Due to cell death.
24
Q
Cytotoxic edema affects … matter.
A
BOTH WHITE + GREY MATTER.
25
Stroke:
Denotes acute loss of neurologic function that occurs when the blood supply to an area of the brain is lost or compromised.
26
Stroke - MRI or CT?
MRI is more sensitive to the EARLY diagnosis of stroke.
27
The normal anatomy of the brain is more easily recognized on:
CT scans - ALTHOUGH MRI is generally the study of choice for detecting and staging intracranial/spinal cord abnormalities because of its superior contrast and soft tissue resolution.
28
What are the Sylvian fissures?
Bilaterally symmetrical and contain CSF --> Separate the temporal from the frontal and parietal lobes.
29
On an UNENHANCED CT scan of the brain, anything that appears "whiite" will generally either be ... or ... in the absence of a metallic foreign body.
Bone (calcium) or blood.
30
Calcifications that may be seen on CT of the brain which are NON pathologic?
1. Pineal gland.
2. Basal ganglia.
3. Choroid plexus.
4. Falx and tentorium.
31
Normal structures that can enhance after administration of iodinated IV contrast?
1. Venous sinuses.
2. Choroid plexus.
3. Pituitary gland and stalk.
32
Metallic densities in the head can cause artifacts on CT scans:
1. Dental fillings.
2. Aneurysm clips.
3. Bullets.
- -> Streak artifacts!
33
Initial evaluation of an MRI of the brain might start with the ...?
T1-sagittal view of the brain.
34
Acute stroke - Study of first choice:
Diffusion-weighted MRI imaging for acute or small strokes, if available.
35
Acute stroke - Other studies:
Non contrast CT can differentiate hemorrhagic from ischemic infarct.
36
Acute and severe headache - Study of first choice:
Non contrast CT to detect SAH.
37
Acute and severe headache - Other studies:
MRA or CTA if SAH is FOUND.
38
Chronic headache - Study of first choice?
MRI without and with contrast.
39
Chronic headaches - Other studies:
CT without and with contrast can be substituted.
40
Seizures - Study of first choice?
MRI with or without contrast.
41
Seizures - Other studies:
CT without and with contrast can be substituted if MRI is not available.
42
Blood - Study of first choice:
Non contrast CT.
43
Blood - Other studies:
US for infants.
44
Head trauma - Study of first choice:
Non enhanced CT is readily available and the study of first choice in head trauma.
45
Head trauma - Other studies:
MRI is better at detecting diffuse axonal injury but requires more time and is not always available.
46
Extracranial carotid disease - Study of first choice:
Doppler US.
47
Extracranial carotid disease - Other studies:
MRA excellent study.
48
Hydrocephalus - Study of first choice:
MRI as initial study.
49
Hydrocephalus - Other studies:
CT for follow-up.
50
Vertigo and dizziness - Study of first choice:
Contrast-enhanced MRI.
51
Vertigo and dizziness - Other studies:
MRA if needed.
52
Masses - Study of first choice:
Contrast-enhanced MRI.
53
Masses - Other studies:
Contrast-enhanced CT if MRI not available.
54
Change in mental status - Study of first choice:
MRI without or with contrast.
55
Change in mental status - Other studies:
CT without contrast is quivalent.
56
Initial CT evaluation of the brain in the emergency setting focuses on ...?
Whether there is mass effect or blood.
57
Skull fractures can be described as ...?
1. Linear.
2. Depressed.
3. Basilar.
58
Most common skull fractures are ...?
Linear.
59
Linear skull fractures ...?
Have little importance other than for the intracranial abnormalities that may have occurred at the time of the fracture, such as an EPIDURAL hematoma.
60
Fractures of the cranial vault are more likely to occur ...?
In the temporal and parietal bones.
61
Depressed skull fractures are more like to be associated with ...?
Underlying brain injury.
62
Which skull fractures are the more serious?
Basilar.
63
Basilar skull fractures consists of?
A linear fracture at the base of the skull.
64
Basilar skull fractures can be associated with ...?
Tears in the dura mater with subsequent CSF leak --> CSF rhinorrhea + otorrhea.
65
Basilar skull fractures can be suspected if ...?
1. There is AIR in the brain = Traumatic pneumocephalus.
2. Fluid in the mastoid air cells.
3. Air-fluid level in the sphenoid sinus.
66
What is the imaging study of choice in evaluating facial fractures?
CT.
67
CT densities in the brain - Hypodense:
1. Fat (not usually present in the head).
2. Air (sinuses).
3. Water (CSF).
68
CT densities of the head - Isodense:
1. Normal brain.
| 2. Some forms of protein (eg subacute subdural hematomas).
69
CT densities of the brain - Hyperdense:
1. Metal (aneurysm clips or bullets).
2. Iodine (after contrast admin).
3. Calcium.
4. Hemorrhage (high protein).
70
What is the MC orbital fracture?
The blow-out fracture --> Direct impact on the orbit --> Sudden increase in intraorbital pressure leading to a fracture of the inferior/medial orbital floor --> Into the maxillary sinus/ethmoid sinus.
71
What happens sometimes in orbital fractures that causes restriction of upward gaze and diplopia?
The inferior rectus muscle can be trapped in the fracture.
72
Recognizing a blow-out fracture of the orbit?
1. Orbital emphysema --> Communication with one of the adjacent air-containing sinuses, either the ethmoid or maxillary sinus.
2. Fracture --> Floor or medial wall of the orbit.
3. Entrapment of fat and/or extraocular muscle --> Projects downward as a soft tissue mass into the top of the maxillary sinus.
4. Fluid (blood) in the maxillary sinus.
73
Tripod fracture:
1. Blunt force to the cheek.
| 2. Separation of the zygoma from the remainder of the face.
74
Bright on T1:
1. Fat.
2. Gadolinium.
3. High protein.
4. Subacute hemorrhage.
75
Dark on T1:
1. Calcification.
2. Air.
3. Chronic hemorrhage.
4. Acute hemorrhage.
5. Water (edema, CSF).
76
Bright on T2:
Water (edema, CSF).
77
Dark on T2:
1. Fat.
2. Calcification.
3. Air.
4. Early subacute hemorrhage.
5. Chronic hemorrhage.
6. Acute hemorrhage.
7. High protein.
78
4 types of intracranial hemorrhage that may be associated with head trauma?
1. Epidural hematoma.
2. Subdural hematoma.
3. Intracerebral hemorrhage.
4. SAH (aneurysms).
79
Epidural hematoma cannot cross ...?
Suture lines (subdural can).
80
Epidural hematomas can cross ...?
THE TENTORIUM (subdural CANNOT).
81
Dura mater?
Composed of two layers:
1. Outer periosteal layer which cannot be separated from the skull.
2. Inner meningeal layer --> Enfolds to form the tentorium and falx.
82
Arachnoid?
The avascular middle layer --> Separated from the dura by a potential space known as the subdural space.
83
Pia mater:
Closely applied to the brain and spinal cord, the pia mater carries blood vessels that supply both; separating the arachnoid from the pia is the subarachnoid space.
84
Together the pia and the arachnoid are called the ...?
Leptomeninges.
85
Chronic subdural hematomas are usually ...?
Low density compared to the remainder of the brain.
86
Intracerebral hemorrhage may occur from ...?
1. Trauma.
2. Aneurysms.
3. Atheromatous disease in small vessels.
4. Vasculitis.
87
Coup injuries are most often due to ...?
Shearing of small intracerebral vessels.
88
Countercoup injuries are ...?
Acceleration/deceleration injuries that occur when the brain is propelled in the opposite direction and strikes the inner surface of the skull.
89
What is a brain contusion?
Hemorrhages with associated edema usually found in the inferior frontal lobes and temporal lobes on or near the surface of the brain.
90
Recognizing traumatic intracerebral hemorrhage on CT:
1. Cerebral contusions --> Multiple, small, well-demarcated areas of high attenuation within the brain parenchyma.
2. Surrounded by a HYPODENSE rim from edema.
3. Intraventricular blood may be present.
4. Mass effect is common --> Herniations.
91
5 types of brain herniations:
1. Subfalcine.
2. Transtentorial.
3. Foramen magnum/tonsillar herniation.
4. Sphenoid herniation.
5. Extracranial herniation.
92
What happens in subfalcine herniation?
The supratentorial brain + lateral ventricle + septum pellucidum --> Herniates beneath the falx and shift across the midline toward the opposite side.
93
What happens in transtentorial herniation?
Usually, the hemispheres are displaced DOWNWARD through the incisura beneath the tentorium compressing the ipsilateral temporal horn --> Dilatation of the contralateral temporal horn.
94
Foramen magnum/tonsillar herniation?
Infratentorial brain is displaced downward through the foramen magnum.
95
Sphenoid herniation?
Supratentorial brain slides over the sphenoid bone either anteriorly (in the case of the temporal bone) or posteriorly (for the frontal lobe).
96
Extracranial herniation?
Displacement of the brain through a defect in the cranium.
97
Diffuse axonal injury is responsible for ...?
The prolonged coma following head trauma and is the head injury with the poorest prognosis.
98
What is most commonly affected in diffuse axonal injury?
The corpus callosum --> Initial CT may be normal.
99
Intraventricular hemorrhage is common in ...?
Premature infants.
100
What is the study of choice in identifying diffuse axonal injury?
MRI.
101
MRI findings in diffuse axonal injury:
1. The small petechial lesions may be bright on T1 images.
2. MC findings are multiple bright areas on T2 images at the TEMPORAL/PARIETAL corticomedullary junction or in the corpus callosum.
102
Some of the clinical signs of increased intracranial pressure are:
1. Papilledema.
2. Diplopia.
3. Headache.
103
Increased ICP is due to ...?
1. Cerebral edema.
| 2. Hydrocephalus.
104
MCCs of cerebral edema in adults:
1. Trauma.
2. HTN --> Intracerebral bleeds and stroke.
3. Masses.
105
Two types of cerebral edema:
1. Vasogenic.
| 2. Cytotoxic.
106
Vasogenic edema represents ...?
Extracellular accumulation of fluid and is the type that is associated with:
1. Malignancy.
2. Infection.
107
Vasogenic edema is due to:
Abnormal permeability of the BBB --> Predominantly affects the WHITE MATTER.
108
Cytotoxic edema represents cellular edema and is associated with ...?
Cerebral ischemia.
109
Cytotoxic edema is due to ...?
Cell death.
110
Cytotoxic edema affects ...?
Both the WHITE and the Gray matter.
111
Recognizing cerebral edema:
1. There is loss of the normal differentiation between gray and white matter.
2. There may be effacement (compression or obliteration) of the normal sulci.
3. Ventricles may be compressed.
4. Herniation of the brain may manifest --> by effacement of the basilar cisterns.
112
Which MRI-type is more sensitive and relative specific for detecting EARLY infarction with the capacity to detect changes within a few MINUTES of the onset of event?
Diffusion-weighted MRI.
113
The MC finding of an acute, non hemorrhagic stroke, less than 24h old, is ...?
A NORMAL CT scan.
114
Recognizing an ischemic stroke, on CT the findings will ...?
Depend on the amount of time that has elapsed since the original event.
115
Recognizing an ischemic stroke - 12-24h?
Indistinct are of low attenuation in a vascular distribution.
116
Recognizing ischemic stroke - >24h?
Better circumscribed lesion with mass effect that peaks at 3 to 5 days and usually disappears by 2 to 4 WEEKS.
117
Recognizing ischemic stroke - 72h?
Though contrast is rarely used in the setting of acute stroke, contrast enhancement typically occurs when the mass effect is waning or has disappeared.
118
Recognizing ischemic stroke - >4weeks:
Mass effect disappears; there is now a well-circumscribed low attenuation lesion with no contrast enhancement.
119
Common areas of hemorrhagic stroke:
1. Basal ganglia.
2. Thalamus.
3. Cerebellum.
4. Pons.
120
Recognizing intracerebral hemorrhage (in general)?
1. Freshly extravasated blood with normal Ht --> Visible as an INCREASED DENSITY on non enhanced CT, IMMEDIATELY after the vent (high protein in the blood).
2. Dissection into the ventricular system may occur in HTN intracerebral bleeds.
3. As the clot begins to form the blood becomes denser for about 3 days because of dehydration of the clot.
4. After the 3rd day, the clot decreases in density and becomes invisible over the next several weeks --> Loses density from the outside in so that is appears to SHRINK.
5. After about 2 MONTHS --> Only a small hypodensity may remain.
121
Why is MRI more sensitive to changing effects in intracerebral hemorrhage?
Because it is sensitive to changing effects of BOTH Hb and IRON.
122
What is the critical size for a berry aneurysm to rupture?
10mm.
123
Changes in the appearance of blood over time in MRI - Hyperacute
T1 --> Isointense.
| T2 --> Bright.
124
Changes in the appearance of blood over time in MRI - Acute 1-3 days?
T1 --> Isointense.
| T2 --> Dark.
125
Changes in the appearance of blood over time in MRI - Early subacute 3-7 days?
T1 --> Bright.
| T2 --> Dark.
126
Changes in the appearance of blood over time in MRI - Late subacute 7-14 days?
T1 --> Bright.
| T2 --> Bright.
127
Changes in the appearance of blood over time in MRI - Chronic >14 days?
T1 --> Dark.
| T2 --> Dark.
128
Lacunar infarcts?
Small cerebral infarcts produced by occlusion of small end arteries accounting for up to 20% of all cerebral infarctions.
129
The term lacunar infarct is reserved for ...?
Low density, cystic lesions, about 5-15mm in size.
130
Causes of SAH?
1. Ruptured aneurysm.
2. Trauma.
3. AV malformations.
4. Breakthrough of an intraparenchymal bleed can also produce SAH.
131
Recognizing a SAH (from a ruptured aneurysm):
1. On CT, blood is hyperdense and may be visualized within the sulci and basal cisterns.
2. The region of the falx may become hyperdense, widened, and irregularly marginated.
3. The greatest concentration of blood indicates the most likely site of the ruptured aneurysm.
132
Other causes of intracerebral hemorrhage:
1. AV malformations.
2. Tumors.
3. Mycotic aneurysms.
4. Amyloid angiopathy.
133
Where is amyloid deposited in amyloid angiopathy?
In the media + adventitia of small-sized vessels, mostly involving the FRONTAL + PARIETAL lobes.
134
Hemorrhages from amyloid angiopathy are usually ...?
LARGE - involving an entire lobe - may occur in several areas simultaneously.
135
Hydrocephalus may be due to several factors:
1. Underabsorption of CSF (communicating hydrocephalus).
2. Restriction of the outflow of CSF from the ventricles (non communicating hydrocephalus.
3. Overproduction of CSF (rare).
136
Hydrocephalus vs cerebral atrophy?
Hydrocephalus --> Ventricles disproportionally dilated compared to SULCI.
Cerebral atrophy --> Both the ventricles + sulci are proportionally enlarged in cerebral atrophy.
137
Which part of the ventricular system is particularly sensitive to increases in CSF pressure?
The temporal horns.
138
Resorption of the CSF through the arachnoid villi may become restricted by ...?
SAH or meningitis.
139
Classically, the 4th ventricle is dilated in ... and normal in size in ... hydrocephalus.
Communicating, non communicating.
140
Communicating hydrocephalus is usually treated with a ...?
Ventricular shunt.
141
Non obstructive hydrocephalus from OVERPRODUCTION of CSF is rare and can occur with a ...?
Choroid plexus papilloma.
142
NPH classical triad?
1. Urinary incontinence.
2. Dementia.
3. Abnormalities of gait.
143
NPH usually occurs in what age group?
50-70.
144
Gliomas are:
The MC PRIMARY, supratentorial, intraaxial mass in an adult.
| --> Account for 35-45% of ALL INTRACRANIAL TUMORS.
145
GBM accounts for ...?
More than half of all gliomas.
146
Astrocytomas account for ...?
About 20%. The remainder split between ependymoma, medulloblastoma, and oligodendroglioma.
147
GBM target group and site?
Males 65-75 --> FRONTAL + TEMPORAL lobes --> WORST prognosis.
148
Recognizing GBM:
1. Necrosis.
2. Butterfly glioma.
3. Considerable VASOGENIC edema + mass effect + enhances with contrast, at least in part.
149
About ...% of intracranial neoplasms are metastases.
40%.
150
Recognizing metastases to the brain?
1. Well-defined, round masses near the gray-white junction.
2. Usually multiple, but can be solitary.
3. Typically HYPODENSE or ISODENSE on non enhanced CT.
4. With IV contrast, they can enhance, sometimes with a pattern of rign enhancement.
5. Most evoke some VASOGENIC edema --> frequently out of proportion to the size of the mass.
151
What is the MC extraaxial mass?
Meningiomas.
152
MC location for a meningioma?
1. Parasaggital, over the convexities.
2. The sphenoid wing.
3. The cerebellopontine angle cistern.
(in decreasing frequency).
153
Multiple meningiomas usually means?
NF2.
154
Recognizing a meningioma on CT?
1. On non enhanced CT, over half are HYPERDENSE to normal brain and about 20% contain calcification.
2. On contrast-enhanced studies --> Meningiomas enhance markedly.
3. They may have edema surrounding them.
155
MC symptom with a Schwannoma?
Hearing loss, but they also produce tinnitus + disturbances in equilibrium.
156
Location of most schwannomas?
Along the course of the 8th nerve within the internal auditory canal at the cerebellopontine angle.
157
Multiple schwanommas means?
NF2.
158
Imaging study of choice for schwanomma?
Contrast-enhanced MRI --> Virtually always enhance, usually homogeneously.
159
MC demyelinating disease?
MS.
160
Imaging findings of MS:
1. The lesions produce discrete, globular foci of high signal intensity (white) on T2.
2. On T1 --> Non enhanced images, they are ISOINTENSE to HYPOINTENSE --> In ACUTE MS, the lesions enhance with gadolinium on T1.
3. Lesions tend to be located with their long axes perpendicular to the ventricular walls.
